Gaheris Rhade originally met Dylan Hunt while working as an operative of Argosy Special Operations, an elite division of the High Guard. Rhade and Hunt were ordered by Constanza Stark to kidnap Ferrin, the tyrannical dictator of Mobius, and deliver him to Commonwealth authoritites so he could stand trial for his acts and a democratic government could be elected. However, complications arose during the mission and Ferrin was killed, paving the way for a new murderous despot to take his place. Following the mission, Rhade received a commendation for saving Dylan's life during the operation. Soon thereafter Hunt was promoted to Captain and given command of the Andromeda Ascendant with Gaheris Rhade as his Executive Officer.

Like most other Nietzscheans, Rhade had begun to resent the Systems Commonwealth for its decision to make peace with the Magog instead of destroying them outright. Anti-Commonwealth sentiments in the Nietzschean community reached a boiling point after the signing of the Treaty of Antares, and soon the calls of the Drago-Kazov pride demanding the Commonwealth's annihilation became a rallying cry for the entire Nietzschean race. The prides felt that after the devastation visited on frontier colonies like Brandenburg Tor, signing a peace agreement with those who had murdered so many of their fellow Nietzscheans was a betrayal that demanded retribution.

Rhade resigned himself to the fact that the Systems Commonwealth had to be destroyed, and recorded history states that Gaheris Rhade sabotaged the Andromeda Ascendant and engaged in a fire fight with Captain Dylan Hunt. Rhade died in this fight, and the Andromeda Ascendant was trapped in the mouth of a black hole, where it, and Captain Hunt, were frozen in time for nearly 300 years.

However, the timeline where Dylan survived is actually an alternate timeline; in the original timeline, Rhade won the fight against Dylan, shooting him immediately upon entering the command room, and it was Rhade who awoke 300 years later over the dead body of his friend. Soon after, he grappled with the Andromeda Ascendant Artificial Intelligence to accept that he was in command despite what he had done. Soon thereafter Rhade discovered that after the Fall, his people the Nietzschean Alliance had descended into civil war, with frequent wars between the prides. Rhade had betrayed the Commonwealth and murdered his best friend for nothing, leaving the galaxy defenceless against the Magog and the Abyss.

Gaheris set out with the crew of the Eureka Maru in an attempt to restore the Systems Commonwealth. However, after a series of betrayals he became frustrated with his inability to form a new Commonwealth. In particular, Rhade refused to allow Nietzscheans prides join the new Commonwealth, since he felt a deep hatred for his people for not replacing the Commonwealth and leaving the galaxy open to devastation by the Magog and the Abyss. When he betrayed the Commonwealth, he fully expected the Nietzschean prides to replace the Commonwealth, rather than descend into civil war; his frustration with Nietzscheans allowed others (namely, the alternate Charlemagne Bolivar) to fracture the unstable peace even more. Even his attempts to hold his crew together failed, with Beka Valentine leaving with Rev Bem despite a romantic relationship with Rhade as she couldn't countenance his more brutal methods, and Tyr Anasazi eventually forcing Rhade to kill him as he became disgruntled with Rhade's demands, Seamus Harper only sticking around because Rhade was the only person he had met who hated Nietzscheans as much as him.

During the Tesseract experiment to save Harper from the Magog eggs inside him, an older Trance Gemini advised him that he may not be the best man for the job, and that his best course of action is to travel back in time and ensure Dylan survives the fight instead. Despite recognising that history would judge him a traitor for what he was about to do, Rhade followed this advice and traveled back in time, killed his younger self to take his place, and ensured that Dylan won the ensuing fire fight in the Command Center by "talking too much". This final selfless act changed history and allowed Dylan to survive and in 300 years time restore the Systems Commonwealth. Somehow, Dylan had a feeling of what Rhade did when he notices the scar on his hand, a scar he did not have in the alternate timeline.

Rhade went down in history as a hero on both sides. The Commonwealth remembered him as one of the first great officers to be lost in the conflict. But the Nietzscheans remembered him as a spy and informant who played a key role in laying their great trap.

Captain Dylan Hunt refers to Rhade's multiple wives, suggesting he possessed a fair amount of status and respect within Nietzchean society. Thus likely he had numerous children and descendants; however they were unaware of his involvement with the Nietzschean Rebellion, as they joined Dylan Hunt's fiancée Sara Riley in forming the colony of Tarazed. Tarazed would be the only place where the Systems Commonwealth would survive after the fall. It is here where Captain Hunt first encountered Rhade's descendant and genetic reincarnation, Admiral Telemachus Rhade supreme commander of Tarazed's home guard. Telemachus would eventually take on the rank of Lt. Commander in the New Systems Commonwealth and take a posting on board the Andromeda Ascendant as Weapons Officer.

By the time of the Nietzschean Rebellion Rhade and Hunt had been close friends for many years. Rhade followed Hunt onto the Andromeda from a previous mission. Hunt had even asked Rhade to be his best man at his wedding. However, Rhade felt that his duty to his people had to outweigh his loyalty to his friend and the Commonwealth, as such he sabotaged the Andromeda Ascendant at the Battle of Hephaistos in an attempt to destroy the vessel before it could warn the Commonwealth about the massive Nietzschean fleet. But he later regretted his actions as it left the Known Worlds open to invasion by the Magog and the deaths of untold billions. His betrayal weighed heavily on his conscience and, in addition to seeing his species turn on one another at the wars end, helped lead to his decision to go back in time and kill his past self and let Dylan start a new Commonwealth.